Mobile track tamper assembly



Nov. 26, 1963 L ssER ETALI- 3,111,909

. MOBILE TRACK TAMPER ASSEMBLY 1 Filed Oct. 27, 1959 2 SheetsSheet 2INVEN TOR. Pam 2 PLA'SSER BY J 0 S THEKR MEIIT' United States Patent3,111,909 MGBILE TRACK TAR HER ASSEMBLY Franz Plasser and Josef Theurer,both of Johannesgasse 3, Vienna, Austria Filed Oct. 2'], 1959, Ser. No.848,947 Claims priority, application Austria Oct. 30, 1958 11 Claims.(Cl. 104-12) The present invention relates to a mobile track tamperassembly for tamping the ballast under a track mounted on spaced ties.

In our copending US. patent application Serial No. 685,863, filedSeptember 24, 1957, now Patent No. 2,971,472, dated February 14, 1961;we have proposed to obtain uniform tamping of the entire roadbed ballastwith a tamper in which the ballast under each tie is firstconventionally tamped by pairs of reciprocating tamping tools and theballast between the ties is then tamped by auxiliary tampers mountedbehind the main tamping tools on the same carriage.

While such a machine produces a very high quality ballast tarnpingoperation with uniform compression of the entire ballast, the mountingof the auxiliary tamper means on the same frame which carried thevertically adjustable main ta-mping tool carrier has caused considerablestructural difiiculties, particularly when two pairs of auxiliarytampers are used to tamp the ballast between the ties on either side ofeach rail. The diificulties arose primarily because the position of theauxiliary tampers must be adjustably spaced from the main tamping toolsto conform the spacing to practically occurring differences in the tiespacing and to make certain that the auxiliary tampers are alwayscentered between adjacent ties. Furthermore, conventional tamperscarrying only the usual pairs of reciprocating tamping tools for campingballast under the ties do not have enough space readily to accommodateauxiliary tamping tools on their carriage frames so that it is difiicultor impossible to change conventional tamping machines to incorporatethis improvement therein.

It is the principal object of the present invention to overcome theseshortcomings of the prior art by providing a mobile track tamperassembly in which the auxiliary tampers are carried on a separatecarriage which is connected to a conventional tamper carriage by alongitudinally adjustable coupling. This adjustable coupling may besimply a flexible elongated element, such as a rope, chain or spring, bywhich the second carriage mounting the auzdliary tamper means isattached to the first carriage mounting the main camping tools.

If desired, the longitudinally adjustable coupling may include anadjustable tension lock consisting, for instance, of a threaded spindleand a nut, which makes it possible to set the length of the coupling,further adjustments during operation then being possible by changing thelength of the coupling. Means equivalent to a spindleand-nut drive, suchas worm gears, rack-'and-pinion drives, etc., may also be used. Such atension lock may be used in conjunction with or instead of a resilientcoupling, i.e. a spring, the position of the second carriage in relationto the first carriage being determined in this case simply by theoperation of the brake means for the two carriages.

In one embodiment of the invention, the longitudinally adjustablecoupling comprises a pressure fluid operated piston-in-cylindermechanism mounted between the two carriages. Compressed air or hydraulicfluid may be used as the pressure fluid to adjust the length of such acoupling.

The second carriage mounting the auxiliary tamper means being coupled tothe first carriage mounting the main tamping tools is simply pulledalong the track as the first carriage proceeds from tie to tie duringthe con- "ice tinuous tamping operation, the longitudinally adjustablecoupling making a variation in the distance between the two carriagespossible. This relative movement between the two carriages may becontrolled by a special operator who observes the position of theauxiliary tamper means and adjusts the distance to center this meansproperly between adjacent ties. In accordance with a preferredembodiment of the invention, however, this relative movement isautomatically controlled in response to the operation of brake means forthe first and second carriage as well as an auxiliary tam-per positionindicator means mounted on the second carriage and indicating thecentering of the auxiliary tamper means between two adjacent ties.

While such an indicator means may obviously have any desired form andcould be mechanically, optically, magnetically or electricallycontrolled by each tie means, i.e. the tie or a tie fastening member, weprefer to use a tactile or tie-probing element constituted by a pivotaltwo-armed lever whose lower end may be engaged by the tie means and thencloses an electrical circuit operating the brake means for the secondcarriage.

Various other preferred features of a highly adjustable and fullyautomated control system for stopping the carriages and centering thesecond carriage in the desired position will be set forth hereinbelow inconnection with a detailed description of certain specific embodimentsof the invention, provided merely for purposes of illustration andwithout in any way limiting its scope.

In the drawing,

FIG. 1 is a side view of a mobile track tamper embodying the principlesof the present invention;

FIGS. 2 and 3 are corresponding fragmentary side views illustrating twospecific embodiments of this invention; and

FIGS. 4 and 5 schematically show two actuating circuits for theautomatic operation of the auxiliary tampers.

Referring now to FIG. 1, there is shown a conventional mobile tracktamper carrying the main tamping tools, such as disclosed and claimed,for instance, in our US. Patent No. 2,876,709. Any other track tamperwith tamping tools adapted to tamp the ballast under the ties may beused, the main tamping tool assembly forming no part of the presentinvention, except inasmuch as it is combined with the auxiliary tampingtool assembly.

In the illustrated embodiment, the main track tamper 'is shown toinclude a carriage 1 in whose forward frame a vertically adjustablymounted tamping tool carrier 4 glides along posts 5. Pairs ofrecopricating t-amping tools 6 are mounted on the carrier 4. The upperends of the tamping tools are linked to arms which are vibrated byeccentric or crank shaft 7 and the lower ends of the tools may bereciprocated toward and away from each other by a pressure mechanismschematically indicated by bydraulic piston-and-cylinder assembly 8. Apower plant 9 is mounted on the carriage 1 to provide the power for allmoving parts of the tamper, including air and/or hydraulic fluidpressure, electric current, etc. All of this structure is conventionaland is, therefore, shown only schematically as part of the combinationof the present invention. This conventional main mobile track tampermoves on wheels 1 along track it) which rests on ties 11 and the ballastroadbed 12.

In accordance with the present invention, an auxiliary tamper isattached to the main mobile track tamper by longitudinally adjustablemeans. In the embodiment of FIG. 1, the auxiliary tamping tools 13 aremounted on a carriage 2 which moves on track ltl with wheels 2. Thelongitudinally adjustable connecting means between the main and theauxiliary tampers is schematically shown as any suitable connectingelement whose length may be adjusted, such as a rope, chain or any otheradjustable coupling through which the auxiliary tamper may be attachedto the main tamper and moved therewith when the main tamper proceedsalong the track and pulls the auxiliary tamper behind it.

As schematically shown, the auxiliary tamping tools may be conventionalvibratory surface tampers 13 carried by rods 13. A rotary eccentricweight 13a is mounted in the vibratory surface tampers 13 and, uponrotation by a motor, vibrates the tamper. The auxiliary tampers aremounted on the carriage 2. Operation of such vibratory surface tampersis effected by vertically reciprocating the same into the illustratedtamping position and then vibrating the same. The illustrated means forthe vertical adjustment of the auxiliary tampers includes a fixedsupport 14 carrying the pivot 15 of a twoarmed lever or rocking arm 15whose one end is linked to the tamping tool carrier or support rod 13'while its other end is linked to piston rod 16. The piston rod isattached to piston 16 which glides in cylinder 17 and divides the sameinto two cylinder chambers. A return spring 17" is mounted in one of thecylinder chambers and biases the piston downwardly to cause the tampingtool 13 to be in an upward rest position above the track. Fluid pressuremay be supplied to the lower cylinder chamber to counteract the bias ofspring 17" and to move the piston upwardly into the position shown inthe drawing when tamping tool 13 is in its operative or tamping positionin contact with the ballast surface.

We prefer to mount two pairs of laterally aligned auxiliary surfacetampers on carriage 2, each pair engaging the ballast adjacent each railof the track, with the rail lying between the tampers of each pair.

It is advisable to arrange a level 2" on carriage 2 to observe thetamped bed. Any desired corrections may then be effected immediately.

FIG. 2 illustrates one specific embodiment of the longitudinallyadjustable coupling between the main mobile track tamper and theauxiliary tamper. Except for the coupling means, all other parts are thesame as in FIG. 1 and have, therefore, been indicated by identicalreference numerals to obviate a repetition of the description thereof.There is shown, in addition, a pressure fluid conduit 17 connected tocylinder 17 and a supply line 13" for the vibrator in tamper 13, theseparts having been omitted from FIG. 1 which is drawn on a smaller scalewhich would make the showing thereof difficult.

In this embodiment, the longitudinally adjustable coupling is simply arope or chain 18 having one end attached t the carriage 1 of the maintamper while its other end is attached to arbor 19 rotatably mounted onsupport 19, the elongated flexible member 18 being guided upwardly toarbor 19 by idling roller 29. As will be obvious, the distance of theauxiliary tamper from the main tamper may be readily adjusted byrotating arbor 19 so as to lengthen or shorten the elongated member 13.

In the embodiment of FIG. 2, the arbor 19 is actuated by an operator whomay observe the position of tamping tool 13 and accordingly rotate arbor19 from seat 21. Wedges or brakes (not shown) may be provided tomaintain the auxiliary tamping tool carriage in a rest position duringtamping.

Economy being a foremost consideration in modern tamping operations andlabor saving devices being the key to such economy, FIG. 3 illustratesan embodiment wherein the auxiliary tamper is automatically operated andno special operator therefor is needed. All parts identical with theparts described in connection with FIGS. 1 and 2 again carry identicalreference numerals to eliminate a repetition of the description thereof.

As shown, the automatic actuating means for the auxiliary tamperincludes a tamping position indicator means consisting of a tactile ortie-probing element constituted by a two-armed lever 22 Whose pivot 22'is mounted on a support on carriage 2. The lower end of lever 22 .4reaches into the range of the track on a level with the ties 11 or tiefastening means 23. The upper end of the lever carries one part ofelectrical contact 25, the other part thereof being carried on thesupport A pressure spring 24 biases lever 22 into a position whereinspring 24 biases lever 22 into a position wherein the contact 25 is openand the electric circuit 34, 35, which will be more fully explainedhereinafter in connection with FIGS. 4 and 5, is closed only when thelower end of the lever encounters the tie means constituted either bytie 11 or tie fastener 23 and is thus pivoted against the pressure ofspring 24.

The support 25 for the pivot 22' of lever 22 and for one part of contact25 is slidably mounted in guide rails 26 so that it may be movedrelatively to the tamping tool 13 and thus provide adjustability.

The pivot 15 of the two-armed lever 15 constituting the means forvertically reciprocating the auxiliary tamping tool carries anelectrical contact member 27 which cooperates with the arcuate contactmember 28 to close the circuit 46, 46". The brake means for theauxiliary tamper is schematically indicated by brake shoe 29 and brakecam 30.

The longitudinally adjustable coupling shown in FIG.

' 3 is a spring member 32 having one end attached to carriage 1 whileits other end is attached to turnbuckle or tension lock 31 which isconnected to carriage 2 and may comprise a threaded spindle and a notmoving along the spindle.

FIG. 4 illustrates one embodiment of an actuating circuit for thecombined tamper of FIG. 3, the previously described parts again carryingidentical reference numerals. As shown, the circuit receives its powerfrom a power source 33 which may be, for instance, an electric storagebattery. Power source 33 is connected to conductor 34 leading to contact25 and continuing therefrom as conductor 35 which leads to time switch36.

Brake 29, 30 of auxiliary tamper carriage 2 is actuated by electromagnet37 which operates valve 38 controlling the supply of compressed air fromair compressor 39 to cylinder 42. In the illustrated position of valve38, corn pressed air is supplied to the brake cylinder 42 throughconduit 41. In the alternate position of the valve, the compressed airis shunted through conduit into the atmosphere. When compressed air issupplied to cylinder 42, piston 43 is moved against the prcssure ofcompression spring 44. Piston rod 43' is linked to rod 45 which actuatesthe brake cam 30 and thus produces a braking action.

The valve actuating electromagnet 37 is connected to conductor 46 comingfrom contact member 28 while conductor 46' delivers current from battery33 to co operating contact member 27.

The electric actuating or control circuit also includes a furtherconductor 47 leading from electric power source 33 to a contact 48arranged on the vertically adjustable main tamping tool carrier 4. Thiscontact is arranged to cooperate with a contact 49 arranged on thecarrier guide post 5 and the circuit from contact 49 to electromagnet 37is completed by conductor 56.

Finally, a brake means is also provided for carriage 1 of the main tracktamper, the illustrated embodiment showing schematically a brake shoe 61and a brake cam 69. This brake is actuated similarly to the actuation ofthe brake of the auxiliary tamper carriage. For this purpose, there isprovided an electromagnet 51 which operates valve 52 controlling thesupply of compressed air from air compressor 53 to cylinder 56. In theillustrated position of the valve, compressed air is supplied to thebrake cylinder 56 through conduit 55. In the alternate position of thevalve, the compressed air is shunted through conduit 54 into theatmosphere. When compressed air is supplied to cylinder 56, piston 57 ismoved against the pressure of compression spring 58. Piston rod 57 islinked to red 59 which actuates the brake cam 64 and thus producesbraking.

The drive control circuit of the main tamper forms no part of thepresent invention and is, therefore, not illusrated, except for theconductor 52 which is connected to one of the windings of electromagnet51 and supplies current thereto from the drive control circuit. A secondwinding of this electromagnet receives current from conductor 63connected to conductor 46". Merely by way of example and in no waylimiting the present invention to such a combination, the main tamperdrive may be designed in accordance with copending US. Patentapplication Serial No. 746,980, filed July 7, 1958, now Patent No.2,976,816, granted March 28, 1961.

As described in this patent, the conductor 62 leading to the solenoidbrake valve 52 is energized, i.e. its control circuit is closed, when atactile sensing element mounted on the first carriage contacts a tie tooperate a switch in the circuit. When the tactile element is out ofcontact with a tie, the switch is opened and the circuit is deenergized,thus leaving conductor 62 without current.

The automatic actuating system illustrated in FIG. 4 operates the tamperof FIG. 3 in the following manner:

Assuming the tamper has arrived at a position wherein the auxiliarytamping tools 13 are positioned intermediate two ties so as to be ableto tamp the ballast therebetween, as shown in FIGS. l3. This will causethe tactile lever 22 to engage the tie 11 or tie bolt 23 and, as thecarriage proceeds, to rock the lever about pivot 22' so that contact 25is closed. Closing of this contact completes the circuit from battery 33over lines 34, 35 to electromagnet 37. Energization of electromagnet 37operates valve 38 to supply compressed air to brake cylinder 42 which,in turn, instantaneously actuates the brake 29, 3-0 to stop the carriage2 of the auxiliary tamper. When carriages l and 2 are yicldinglycoupled, as by spring 32, stoppage of the auxiliary tamper carriage maybe effected independently from the movement of the main tamper carriage.A suitably set time switch 36 in conductor 35 limits the energy supplyto electromagnet 37. However, in the automated operating cycle of thetamper, pressure fluid has meanwhile been supplied through conduit 17 tocylinder 17 to force the auxiliary tamping tool 13 downwardly into theillustrated position wherein contact parts 27 and 23 cooperate to closethe circuit 46', 45 from the battery 33 to electromagnet 37. In thismanner, the electromagnet remains energized and the brake closed evenafter time switch 36 has disconnected the power supply source from theelectromagnet by way of conductor 35.

As the tamping operations of auxiliary tamping tools 13 and main tampingtools 6 are completed, it is essential to prevent forward movement ofthe carriages 1 and 2 before the tamping tools are moved upwardly again;otherwise, the tamping tools would damage the ties and become damagedthemselves as the carriages proceed with the tamping tools in contactwith or immersed in the ballast. This is accomplished by keepingelectromagnet 37 energized through lines 46, as" as long as the rockingarm is pivoted to maintain tamping tool 13 in contact with the ballast.In this position, contact 27, 28 is closed and this contact will openonly after the contact hand 27 has moved off arcuate contact rail 28,which corresponds to the upper or rest position of tamping tool 13. Theelectromagnet will remain energized even in the position as long as themain tamping tool carrier 4 is in its lower or tampiru position becauseit still receives current from battery 3.3 through lines 47, Sit, thecircuit being closed by cooperating contacts 48, 49. Thus, theelectromagnet 37 is de-energized only after both the auxiliary and themain tamping tools have been lifted out of their tamping position. Thisde-energization will deactivate the brake 29, 3b and thus enable thecarriage 2 to proceed.

The main carriage l is also stopped as long as the tamping tool 13 is inits lower or tamping position. In

this position, the energized conductor 45 supplies current to one of thewindings of electromagnet 51 via branch line 63 which connects thiswinding with conductor 46. Thus, even if the main tamper drive controlcircuit had dc-energized line 62 so as to cut off current from one ofthe windings of electromagnet 51, the carriage 1 would still remainstopped by brake 6t 61 because the electromagnet would remain energizedas long as the auxiliary tamping tool is not lifted to disengage contactmembers 27, 28.

After all the tamping tools have been lifted, the brakes areautomatically disengaged and the tamping assembly may proceed forwardlyto the next tamping position where the above-described braking operationis repeated.

FIG. 5 illustrates an embodiment of the invention wherein thelongitudinally adjustable coupling between carriages 1 and 2 consists ofa piston-in-cylinder mechanism. It is shown in connection with anautomatic actuating system although this mechanism may obviously becontrolled in any desired manner to adjust the distance or spacingbetween the carriages and thus between the main tamping tools and theauxiliary tamping tools.

As shown, the coupling includes a cylinder 64 linked to carriage 1 at 64and a piston 65 whose piston rod 65 has its outer end attached to aturnbuckle or tension lock 31 interposed between the coupling andcarriage 2. A compression spring 67 is mounted in one chamber of thecylinder 64 while the other chamber may be supplied with a pressurefluid through conduit 66. The approximate spacing between the carriagesis effected by means of the tension lock 31 according to the prevailingtie spacing of the track portion to be tamped, the length of thecoupling being so adjusted that it corresponds to the maximum spacing ofthe ties. The length of the coupling can then be shortened during thetamping operation if and when the need therefor arises by supplyingpressure fluid to cylinder 64.

The pressure fluid supply to cylinder 64 is controlled by valve 69 whichis actuated by electromagnet 68. The valve is interposed betweenconduits 66 and 7t the latter conduit receiving hydraulic fluid frompump 71. A throttle valve 72 is mounted in conduit 70. The maxi mumpressure is limited by provision of a branch conduit connected to supplyconduit 7 fl and carrying relief valve 74. When electromagnet 68 isde-energized, the valve 69 is closed and the pump delivers the fluidthrough the conduit 75 into the return or idling conduit 77. Fluidreturning from the cylinder 64 under the pressure of compression spring67 also enters into the return conduit 77 through conduit 76.

The electromagnet 68 may be energized through conductor 78 whichconnects its winding to the contact 25 which is closed by tactileelement 22, as hereinabove explained. A switch 3% is mounted in theconductor 78 and may be actuated by electromagnet 79. The latterelecromagnet is connected to the conductor 62 of the main drive circuit,as described hereinabove. Furthermore, another conductor 82 connects thecontact 25, which is here formed by a four-way switch, to battery 33.

The embodiment illustrated in FIG. 5 operates as follows:

Assuming carriage l of the main tamper has reached a desired position inwhich the reciprocating tamping tool pairs tamp the ballast under a tiebut the carriage of the auxiliary tamper is not properly positionedbecause the coupling has been set for a maximum tie spacing while thedistance of the ties at this particular location is smaller. To centerthe auxiliary tamping tools properly in such a situation, the carriage 2must be pulled a little closer to carriage 1.

As long as the tactile element 22 is not pivoted by a tie or tiefastening means, contact 25 interrupts the circuit 34, 35 but current issupplied to switch ill? from battery 33 through lines 82 and 78.However, electromagnet 68 for valve 69 is energized only if switch 8i)is closed and this happens only after the main tamper has been stoppedso that conductor 62 is without current, the winding of switch actuatingelectromagnet 79 being connected to conductor 62 by conductor 81. Aspreviously explained, conductor 62 is supplied with power only when themain drive circuit is in position for driving the tamper carriage. Oncethe main carriage is stopped and conductor 62. is without current,electromagnet 79 is deenergized and contact 83 is closed, as shown. Thiscauses energization of electromagnet 63, concomitant actuation of valve69, hydraulic fluid supply to cylinder 64 and a corresponding pulling ofcarriage 2 closer to carriage 1. As soon, however, as the tactile lever22 is rocked by contact with a tie means, which indicates the desiredcentering of the auxiliary tamping tools between two ties, the switch 25interrupts circuits 82, 73 and closes circuit 34, 35. This producesde-energization of electromagnet 68 and concomitant stoppage of furtherpressure fluid supply to cylinder 64 while simultaneously initiating thebraking of carriage 2, as hereinabove described. In this manner, thecarriage is properly positioned for tamping of the ballast between theties.

Many variations and modifications of the structure may occur to theskilled in the art, particularly after benefitting from our teaching,without departing from the spirit and scope of the present invention asdefined by the appended claims. More particularly, fully automatedactuation of the auxiliary tamper in dependency of the tamping operationof the main tamper may be effected, which will greatly simplify theoperation of the machine.

What we claim is:

l. A mobile track tamper assembly for tamping the ballast under a trackmounted on spaced ties, comprising a first carriage, main tamping toolsmounted on said first carriage for tamping the ballast under said tiesadjacent the track, a second carriage movable on said track in unisonwith the first carriage, at least one auxiliary tamping tool mounted onsaid second carriage for tamping the ballast between adjacent ones ofsaid spaced ties, a longitudinally adjustable coupling connecting thesecond carriage to the back of the first carriage, said coupling havinga predetermined length, and means for adjusting the coupling within saidlength.

2. A mobile track tamper assembly for tamping the ballast under a trackmounted on spaced ties, comprising a first carriage, main tamping toolsmounted on said first carriage for tamping the ballast under said tiesadjacent the track, a second carriage movable on said track in unisonwith the first carriage, at least one auxiliary tamping tool mounted onsaid second carriage for tamping the ballast between adjacent ones ofsaid spaced ties, a longitudinally adjustable coupling connecting thesecond carriage to the back of the first carriage, said couplingincluding a tension lock and having a predetermined length adjusted bysaid tension lock.

3. A mobile track tamper assembly for tamping the ballast under a trackmounted on spaced ties, comprising a first carriage, main tamping toolsmounted on said first carriage for tamping the ballast under said tiesadjacent the track, a second carriage movable on said track in unisonwith the first carriage, at least one auxiliary tamping tool mounted onsaid second carriage for tamping the ballast between adjacent ones ofsaid spaced ties, a longitudinally adjustable resilient coupling elementconnecting the second carriage to the back of the first carriage, saidcoupling having a predetermined length, and means for adjusting thecoupling within said length.

4. A mobile track tamper assembly for tamping the ballast under a trackmounted on spaced ties, comprising a first carriage, main tamping toolsmounted on said first carriage for tamping the ballast under said tiesadjacent the track, a second carriage movable on said track in unisonwith the first carriage, at least one auxiliary tamping tool mounted onsaid second carriage for tamping the ballast between adjacent ones ofsaid spaced ties, and a longitudinally adjustable piston-in-cylindercoupling connecting the second carriage to the back of the firstcarriage, including means for supplying pressure fluid to the cylinderof the coupling.

5. A mobile track tamper assembly for tamping the ballast under a trackmounted on spaced ties, comprising a first carriage, main tamping toolsmounted on said first carriage for tamping the ballast under said tiesadjacent the track, a second carriage movable on said track in unisonwith the first carriage, at least one auxiliary tamping tool mounted onsaid second carriage for tamping the ballast between adjacent ones ofsaid spaced ties, an auxiliary tamping tool position indicator meansmounted on the second carriage for indicating the centering of theauxiliary tamping tool between two adjacent ties, said indicator meansincluding a two-armed lever having a lower end reaching to the plane ofthe tie, said second carriage being provided with a brake means, anelectrical brake actuating circuit, and a two-part contact in saidcircuit, one part of said contact being mounted on the upper end of thetwo-armed lever whereby the contact is closed when the lower end of thelever is moved on contact with one of said ties, a longitudinallyadjustable coupling connecting the second carriage to the back of thefirst carriage, said coupling having a predetermined length, and meansfor adjusting the coupling within said length.

6. A mobile track tamper assembly for tamping the ballast under a trackmounted on spaced ties, comprising a first carriage, main tamping toolsvertically adjustably mounted on said first carriage for tamping theballast under said ties adjacent the track, a second carriage movable onsaid track in unison with the first carriage, at least one auxiliarytamping tool vertically adjustably mounted on said second carriage fortamping the ballast between adjacent ones of said spaced ties, a brakemeans for said second carriage, an auxiliary tamping tool positionindicator means mounted on said second carriage for indicating thecentering of the auxiliary tamping tool between two adjacent ties, anelectrical brake actuating circuit, three switch means for closing saidcircuit, each of said switch means being responsive, respectively, tothe vertical upward movement of the main and auxiliary tamping tools andto the auxiliary tamping tool position indicator means when it indicatescentering of the auxiliary tamping tool, whereby said circuit will beclosed and the brake means actuated only when the tamping tools arevertically upwardly adjusted and the auxiliary tamping tool is centered,a longitudinally adjustable coupling connecting the second carriage tothe back of the first carriage, said coupling having a predeterminedlength, and means for adjusting the coupling within said length.

7. The mobile track tamper assembly of claim 6, further comprising apressure fluid operated means for actuating the brake means, a valvecontrolling the pressure fluid supply to said pressure fluid operatedmeans, and an electromagnet for operating the valve, said electromagnetbeing arranged in the electrical brake actuating circuit and beingenergized upon closing of the circuit.

8. A mobile track tamper assembly for tamping the ballast under a trackmounted on spaced ties, comprising a first carriage, main tamping toolsmounted on said first carriage for tamping the ballast under said tiesadjacent the track, a second carriage movable on said track in unisonwith the first carriage, at least one auxiliary tamping tool mounted onsaid second carriage for tamping the ballast between adjacent ones ofsaid spaced ties, a longitudinally adjustable piston-in-cylindercoupling including a tension lock connecting the second carriage to theback of the first carriage, the tension lock adjusting the length of thecoupling to the maximum spacing of the ties, and a pressure fluid supplyfor the cylinder of the coupling to move the piston in the cylinder andto shorten the coupling upon supplying pressure fluid to the cylinder.

9. A mobile track tamper assembly for tamping the ballast under a trackmounted on spaced ties, comprising a first carriage movable on saidtrack, main tamping tools mounted on said first carriage for tamping theballast under said ties adjacent the track, a second carriage movable onsaid track in unison with the first carriage, at least one auxiliarytamping tool mounted on said second carriage for tamping the ballastbetween adjacent ones of said spaced ties, a longitudinally adjustablepiston-in-cylinder coupling including a tension lock connecting thesecond carriage to the back of the first carriage, the tension lockadjusting the length of the coupling to the maximum spacing of the ties,a pressure fluid supply for the cylinder of the coupling to move thepiston in the cylinder and to shorten the coupling upon supplyingpressure fluid to the cylinder, brake means for the first carriage,another brake means for the second carriage, means actuating thepressure fluid supply in response to the actuation of the brake meansfor the first carriage and means for discontinuing the pressure fluidsupply in response to the actuation of the brake means for the secondcarriage.

10. The mobile track tamper assembly of claim 9, further comprising anauxiliary tamping tool position indicator means mounted on the secondcarriage for indicating the centering of the auxiliary tamping toolbetween two adjacent ties, the means for discontinuing the pressurefluid supply being also responsive to the operation of the indicatormeans.

11. The mobile track tamper assembly of claim 10, wherein said means foractuating and discontinuing the pressure fluid supply includes anelectrical actuating circuit opened and closed by switch meansresponsive to said brake and indicator means, an electromagnetenergizable by the closing of the circuit and a valve operated by saidelectromagnet.

References Cited in the file of this patent UNITED STATES PATENTS1,415,194 Robinson May 9, 1922 1,684,109 Peterson Sept. 11, 19282,497,682 Mertz Feb. 14, 1950 2,736,268 Yohe Feb. 28, 1956 2,876,709Plasser et al. Mar. 10, 1959 FOREIGN PATENTS 126,037 Australia Nov. 10,1947 794,235 Great Britain Apr. 30, 1958 1,029,167 France Mar. 4, 1953

1. A MOBILE TRACK TAMPER ASSEMBLY FOR TAMPING THE BALLAST UNDER A TRACKMOUNTED ON SPACED TIES, COMPRISING A FIRST CARRIAGE, MAIN TAMPING TOOLSMOUNTED ON SAID FIRST CARRIAGE FOR TAMPING THE BALLAST UNDER SAID TIESADJACENT THE TRACK, A SECOND CARRIAGE MOVABLE ON SAID TRACK IN UNISONWITH THE FIRST CARRIAGE, AT LEAST ONE AUXILIARY TAMPING TOOL MOUNTED ONSAID SECOND CARRIAGE FOR TAMPING THE BALLAST BETWEEN ADJACENT ONES OFSAID SPACED TIES, A LONGITUDINALLY ADJUSTABLE COUPLING CONNECTING THESECOND CARRIAGE TO THE BACK OF THE FIRST CARRIAGE, SAID COUPLING HAVINGA PREDETERMINED LENGTH, AND MEANS FOR ADJUSTING THE COUPLING WITHIN SAIDLENGTH.